Michajlovskij N, Strbák V, Földes O
Experientia. 1978 Mar 15;34(3):409-10. doi: 10.1007/BF01923064.
The administration of thiocyanate to rats caused a significant increase of serum free thyroxine fraction, which coincided with the significant decrease of TSH level. The other components (AFT4, T4, T3) in serum at this time were decreased or unchanged. The finding suggests the role of free thyroxine fraction in feed-back regulation of TSH secretion.